Carbon dioxide recovery system and method

Abstract

The carbon dioxide recovery system includes: a first steam line 21 a through which low-pressure steam 14 L is fed from an intermediate-pressure turbine 12 to a low-pressure turbine 13 ; a second steam line 21 b into which the low-pressure steam 14 L is branched from the first steam line 21 a ; a first regulation valve V 1 for regulating the opening of the low-pressure steam 14 L from 100% to 0%; a second regulation valve V 2 for regulating the opening of the low-pressure steam 14 L from 0% to 100% depending on the amount of control provided to the first regulation valve V 1 ; a first auxiliary turbine 22 A for recovering power using the low-pressure steam 14 L being fed; and a first steam feed line 25 L through which exhaust steam 23 discharged from the first auxiliary turbine 22 A is supplied as a source of heat to a reboiler 24.

The invention claimed is: 
     
       1. A carbon dioxide recovery system, comprising:
 a high-pressure turbine, an intermediate-pressure turbine, and a low-pressure turbine; 
 a boiler for producing steam to drive the turbines; 
 a carbon dioxide recovery unit including a carbon dioxide absorber for allowing a carbon dioxide absorbent to absorb and reduce carbon dioxide in a combustion flue gas discharged from the boiler and a carbon dioxide regenerator for regenerating the carbon dioxide absorbent having absorbed carbon dioxide as a regenerated carbon dioxide absorbent; 
 a first steam line through which low-pressure steam is fed from the intermediate-pressure turbine to the low-pressure turbine; 
 a second steam line into which the low-pressure steam is branched from the first steam line; 
 a first regulation valve disposed on the first steam line to regulate an opening of an amount of steam of the low-pressure steam from 100% to 0%; 
 a second regulation valve disposed on the second steam line to regulate an opening of an amount of steam of the low-pressure steam from 0% to 100% depending on the amount of control provided to the first regulation valve; 
 a first auxiliary turbine coupled to the second steam line to recover power using the low-pressure steam being fed; 
 a first steam feed line through which exhaust steam discharged from the first auxiliary turbine is employed to be fed as a source of heat to a reboiler which is used to regenerate the carbon dioxide absorbent having absorbed carbon dioxide in the carbon dioxide regenerator; 
 a bleed line through which the low-pressure steam having been bled from the first auxiliary turbine is fed to the low-pressure turbine; and 
 a control device configured to control driving of the first auxiliary turbine by controlling an opening from 100% to 0% and from 0% to 100% in carbon dioxide recovery and non-recovery modes in response to a variation in operation load of the boiler or the turbines while a pressure of the exhaust steam supplied to the reboiler is maintained to take on a permissible value for a reboiler optimum pressure (about 0.33 MPa±0.05 MPa) with the first regulation valve and the second regulation valve being operated in response to each other. 
 
     
     
       2. A carbon dioxide recovery method including using the carbon dioxide recovery system according to  claim 1  to recover carbon dioxide which has been absorbed in the carbon dioxide absorbent.